32 results on '"Florence K. A. Gregson"'
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2. Correction to 'Accurate Representations of the Microphysical Processes Occurring during the Transport of Exhaled Aerosols and Droplets'
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Jim S. Walker, Justice Archer, Florence K. A. Gregson, Sarah E. S. Michel, Bryan R. Bzdek, and Jonathan P. Reid
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Chemistry ,QD1-999 - Published
- 2021
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Catalog
3. Not all types of secondary organic aerosol mix: two phases observed when mixing different secondary organic aerosol types
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Fabian Mahrt, Long Peng, Julia Zaks, Paul E. Ohno, Natalie R. Smith, Florence K. A. Gregson, Yi Ming Qin, Celia L. Faiola, Sergey A. Nizkorodov, Markus Ammann, Scot T. Martin, and Allan K. Bertram
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Atmospheric aerosol particles play an important role for air quality and climate. Secondary organic aerosol (SOA) make up a significant mass fraction of these particles. SOA particles mostly forms from oxidation of gases, followed by gas-particle conversion of the oxidation products. Due to the variety of precursors and oxidation pathways involved in SOA formation, atmospheric SOA rank among the least understood aerosol types. To assess the impacts of SOA particles on air pollution and climate, knowledge of the number of phases in internal mixtures of different SOA types is critical. For example, gas-particle partitioning of organic species, and thus ultimately ambient SOA mass concentration, strongly depend on the number of phases in SOA particles. Atmospheric models traditionally assumed that different SOA types form a single condensed organic phase when internally mixed in individual particles. In case of mixed SOA particles with a single condensed phase uptake of semi-volatile vapors are enhanced, due to a lowering of the activities in the organic aerosol phase, and hence a lowering of the equilibrium partial pressure. By contrast, the equilibrium partial pressure is greater if the different SOA types form separate phases due to repulsive intermolecular forces between immiscible organic molecules. Consequently, enhancement of vapor uptake and ambient SOA mass concentrations will be smaller or absent in the case of phase-separated SOA particles.Here, using fluorescence microscopy, we directly observed the number of phase in individual particles containing mixtures of different SOA types. A total of 6 different SOA types were generated in environmental chambers from oxidation of single precursors. This included both biogenic and anthropogenic SOA types, having elemental oxygen-to-carbon (O/C) ratios between 0.34 and 1.05, covering values characteristic for aged and fresh atmospheric SOA. The number of phases of all possible internal mixtures of two different SOA types, termed SOA+SOA particles, was investigated as a function of humidity between 90% and 0% relative humidity (RH). We found that the number of phases was independent of RH within the range investigated and that 6 out of 15 SOA+SOA mixtures resulted in particles with two condensed organic phases. The observation of phase separated SOA+SOA particles challenges the approach of assuming a single condensed organic phase when representing SOA formation in atmospheric models. Specifically, we demonstrate that the difference in the average O/C ratio between the two SOA types of a mixture (ΔO/C) is a good predictor of the number of phases in particles that are internal mixtures of different SOA types: two-phase SOA+SOA particles formed for ΔO/C ≥ 0.47, while one-phase SOA+SOA particles formed for ΔO/C < 0.47. This threshold ΔO/C provides a simple, yet powerful parameter to predict whether mixtures of fresh and aged SOA particles form one- or two-phase particles in models. more...
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- 2023
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4. Liquid-liquid phase separation and viscosity in biomass burning organic aerosol and climatic impacts
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Florence K. A. Gregson, Nealan G. A. Gerrebos, Meredith Schervish, Sepehr Nikkho, Elijah G. Schnitzler, Carley Schwartz, Christopher Carlsten, Jonathan P. D. Abbatt, Saeid Kamal, Manabu Shiraiwa, and Allan K. Bertram more...
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Smoke particles generated by burning biomass consist mainly of organic aerosol, referred to as biomass-burning organic aerosol (BBOA). BBOA influences the climate by scattering and absorbing solar radiation or acting as nuclei for cloud formation. The viscosity and the phase behavior (i.e. the number and type of phases present in a particle) are properties of BBOA that are expected to impact several climate-relevant processes but remain highly uncertain. We studied the phase behavior of BBOA using fluorescence microscopy, and showed that BBOA particles comprise two organic phases (a hydrophobic and a hydrophilic phase) across a wide range of atmospheric relative humidity (RH). We determined the viscosity of the two phases using a photobleaching method, and showed that the two phases possess different RH-dependent viscosities. The viscosity of the hydrophobic phase is largely independent of the RH from 0 to 95%. For temperatures less than 230 K, the hydrophobic phase is glassy (viscosity > 1012 Pa s) at RHs below 95%, with possible implications for heterogeneous reaction kinetics and cloud formation in the atmosphere. Using a kinetic multi-layer model (KM-GAP), we investigated the effect of two phases on the atmospheric lifetime of brown carbon within BBOA, which is a climate-warming agent. We showed that the presence of two phases can increase the lifetime of brown carbon in the planetary boundary layer and polar regions compared to previous modelling studies. Hence, liquid-liquid phase separation can lead to an increase in the predicted warming effect of BBOA on climate. more...
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- 2023
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5. Quantitative evaluation of aerosol generation during manual facemask ventilation
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Florence K. A. Gregson, Fergus Hamilton, Jonathan P. Reid, Anthony E. Pickering, F. McGain, Bryan R. Bzdek, Ruhi S Humphries, Andrew J Shrimpton, Tim Cook, Rana S. Dhillon, Jules Brown, and David Scott more...
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Adult ,Male ,Leak ,Operating theatres ,manual ventilation ,medicine.medical_treatment ,facemask ventilation ,SARS-COV-2 ,Severe Acute Respiratory Syndrome ,SARS‐CoV‐2 ,law.invention ,COVID‐19 ,law ,Tidal breathing ,Humans ,Medicine ,aerosol-generating procedure ,Respiratory system ,aerosol‐generating procedure ,Aged ,business.industry ,Core component ,Masks ,COVID-19 ,Respiratory Aerosols and Droplets ,Original Articles ,Middle Aged ,Aerosol ,Anesthesiology and Pain Medicine ,Cough ,Severe acute respiratory syndrome-related coronavirus ,Anesthesia ,Ventilation (architecture) ,Original Article ,Female ,Airway management ,AERATOR ,business - Abstract
SummaryManual facemask ventilation, a core component of elective and emergency airway management, is classified as an aerosol generating procedure. This designation is based on a single epidemiological study suggesting an association between facemask ventilation and transmission from the SARS 2003 outbreak. There is no direct evidence to indicate whether facemask ventilation is a high-risk procedure for aerosol generation. We conducted aerosol monitoring during routine facemask ventilation, and facemask ventilation with an intentionally generated leak, in anaesthetised patients with neuromuscular blockade. Recordings were made in ultraclean theatres and compared against the aerosol generated by the patient’s own tidal breathing and coughs. Respiratory aerosol from tidal breathing was reliably detected above the very low background particle concentrations (191 (77-486 [3.8-1313]) versus 2.1 (0.7-4.6 [0-12.9] particles.l-1 median(IQR)[range], n=11, p=0.002). The average aerosol concentration detected during facemask ventilation both without a leak (3.0 particles.l-1 (0 – 9 [0-43])) and with an intentional leak (11 particles.l-1 (7.0 – 26 [1-62])) was 64-fold and 17-fold lower than that of tidal breathing (p=0.001 and p=0.002 respectively). The peak particle concentration during facemask ventilation both without a leak (60 particles.l-1 (0 – 60 [0-120])) and with a leak (120 particles.l-1 (60 – 180 [60-480]) were respectively 20-fold and 10-fold lower than a cough (1260 particles (800 – 3242 [100-3682]), p=0.002 and p=0.001 respectively). This study demonstrates that facemask ventilation, even performed with an intentional leak, does not generate high levels of bioaerosol. On the basis of this evidence, facemask ventilation should not be considered an aerosol generating procedure. more...
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- 2021
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6. Identification of the source events for aerosol generation during oesophago-gastro-duodenoscopy
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Bryan R. Bzdek, Tim M Cook, Jonathan P. Reid, Fergus Hamilton, Anthony E. Pickering, Florence K. A. Gregson, Jules Brown, Andrew J Shrimpton, and Dimitri J Pournaras
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Adult ,endoscopic procedures ,Coronavirus disease 2019 (COVID-19) ,Endoscopy, Gastrointestinal ,Peak concentration ,03 medical and health sciences ,0302 clinical medicine ,Gastro ,Cough/etiology ,Tidal breathing ,Gastroscopy ,Humans ,Medicine ,Burping ,Prospective Studies ,030212 general & internal medicine ,Particle Size ,Respiratory system ,Duodenoscopy ,Endoscopy, Gastrointestinal/adverse effects ,Aerosols ,business.industry ,Gastroenterology ,COVID-19 ,Endoscopy ,respiratory system ,Aerosol ,Cough ,Anesthesia ,030211 gastroenterology & hepatology ,Esophagoscopy ,medicine.symptom ,AERATOR ,business - Abstract
ObjectiveTo determine if oesophago-gastro-duodenoscopy (OGD) generates increased levels of aerosol in conscious patients and identify the source events.DesignA prospective, environmental aerosol monitoring study, undertaken in an ultraclean environment, on patients undergoing OGD. Sampling was performed 20 cm away from the patient’s mouth using an optical particle sizer. Aerosol levels during OGD were compared with tidal breathing and voluntary coughs within subject.ResultsPatients undergoing bariatric surgical assessment were recruited (mean body mass index 44 and mean age 40 years, n=15). A low background particle concentration in theatres (3 L−1) enabled detection of aerosol generation by tidal breathing (mean particle concentration 118 L−1). Aerosol recording during OGD showed an average particle number concentration of 595 L−1with a wide range (3–4320 L−1). Bioaerosol-generating events, namely, coughing or burping, were common. Coughing was evoked in 60% of the endoscopies, with a greater peak concentration and a greater total number of sampled particles than the patient’s reference voluntary coughs (11 710 vs 2320 L−1and 780 vs 191 particles, n=9 and p=0.008). Endoscopies with coughs generated a higher level of aerosol than tidal breathing, whereas those without coughs were not different to the background. Burps also generated increased aerosol concentration, similar to those recorded during voluntary coughs. The insertion and removal of the endoscope were not aerosol generating unless a cough was triggered.ConclusionCoughing evoked during OGD is the main source of the increased aerosol levels, and therefore, OGD should be regarded as a procedure with high risk of producing respiratory aerosols. OGD should be conducted with airborne personal protective equipment and appropriate precautions in those patients who are at risk of having COVID-19 or other respiratory pathogens. more...
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- 2021
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7. Are aerosols generated during lung function testing in patients and healthy volunteers? Results from the AERATOR study
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George W Nava, Sadiyah Sheikh, Jules Brown, Nick A Maskell, Jonathan P. Reid, Fergus Hamilton, Bryan R. Bzdek, Colleen Riley, Florence K. A. Gregson, James W. Dodd, and David T Arnold
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Aerosols ,Pulmonary and Respiratory Medicine ,Spirometry ,medicine.diagnostic_test ,business.industry ,Masks ,Respiratory infection ,respiratory system ,Healthy Volunteers ,Respiratory Function Tests ,Aerosol ,Pulmonary function testing ,Anesthesia ,Breathing ,medicine ,Humans ,In patient ,Particle Size ,Respiratory system ,business ,Lung ,Lung function - Abstract
Pulmonary function tests are fundamental to the diagnosis and monitoring of respiratory diseases. There is uncertainty around whether potentially infectious aerosols are produced during testing and there are limited data on mitigation strategies to reduce risk to staff. Healthy volunteers and patients with lung disease underwent standardised spirometry, peak flow and FENO assessments. Aerosol number concentration was sampled using an aerodynamic particle sizer and an optical particle sizer. Measured aerosol concentrations were compared with breathing, speaking and voluntary coughing. Mitigation strategies included a standard viral filter and a full-face mask normally used for exercise testing (to mitigate induced coughing). 147 measures were collected from 33 healthy volunteers and 10 patients with lung disease. The aerosol number concentration was highest in coughs (1.45–1.61 particles/cm3), followed by unfiltered peak flow (0.37–0.76 particles/cm3). Addition of a viral filter to peak flow reduced aerosol emission by a factor of 10 without affecting the results. On average, coughs produced 22 times more aerosols than standard spirometry (with filter) in patients and 56 times more aerosols in healthy volunteers. FENO measurement produced negligible aerosols. Cardiopulmonary exercise test (CPET) masks reduced aerosol emission when breathing, speaking and coughing significantly. Lung function testing produces less aerosols than voluntary coughing. CPET masks may be used to reduce aerosol emission from induced coughing. Standard viral filters are sufficiently effective to allow guidelines to remove lung function testing from the list of aerosol-generating procedures. more...
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- 2021
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8. Not All Types of Secondary Organic Aerosol Mix: Two Phases Observed When Mixing Different Secondary Organic Aerosol Types
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Fabian Mahrt, Long Peng, Julia Zaks, Yuanzhou Huang, Paul E. Ohno, Natalie R. Smith, Florence K. A. Gregson, Yiming Qin, Celia L. Faiola, Scot T. Martin, Sergey A. Nizkorodov, Markus Ammann, and Allan K. Bertram more...
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Atmospheric Science ,behavioral disciplines and activities - Abstract
Secondary organic aerosol (SOA) constitutes a large fraction of atmospheric aerosol. To assess its impacts on cli-mate and air pollution, knowledge of the number of phases in internal mixtures of different SOA types is required. Atmospheric models often assumed that different SOA types form a single phase when mixed. Here, we present visual observations of the number of phases formed after mixing different anthropogenic and biogenic SOA types. Mixing SOA types generated in environmental chambers with oxygen-to-carbon (O / C) ratios between 0.34 to 1.05, we found six out of fifteen mixtures of two SOA types to result in two phase particles. We demonstrate that the number of phases depends on the difference in the average O / C ratio between the two SOA types (Δ(O / C)). Using a threshold Δ(O / C) of 0.47, we can predict the phase behavior of over 90 % of our mixtures, with one- and two-phase particles predicted for Δ(O / C) < 0.47 and Δ(O / C) ≥ 0.47, respectively. This Δ(O / C) threshold further allows to predict if mixtures of fresh and aged SOA form one- or two-phase particles in the atmos-phere. In addition, we show that phase separated SOA particles form when mixtures of volatile organic compounds emitted from real trees are oxidized. more...
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- 2022
9. Supplementary material to 'Not All Types of Secondary Organic Aerosol Mix: Two Phases Observed When Mixing Different Secondary Organic Aerosol Types'
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Fabian Mahrt, Long Peng, Julia Zaks, Yuanzhou Huang, Paul E. Ohno, Natalie R. Smith, Florence K. A. Gregson, Yiming Qin, Celia L. Faiola, Scot T. Martin, Sergey A. Nizkorodov, Markus Ammann, and Allan K. Bertram more...
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- 2022
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10. Drying Kinetics and Particle Formation from Dilute Colloidal Suspensions in Aerosol Droplets
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Jonathon P Reid, Jim S. Walker, J. Archer, Daniel A Hardy, and Florence K. A. Gregson
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endocrine system ,Materials science ,Colloidal silica ,Evaporation ,02 engineering and technology ,Surfaces and Interfaces ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,complex mixtures ,01 natural sciences ,0104 chemical sciences ,Aerosol ,Colloid ,Chemical engineering ,Spray drying ,Electrochemistry ,Particle ,General Materials Science ,Relative humidity ,Microparticle ,0210 nano-technology ,Spectroscopy - Abstract
Industrial processes such as spray drying of pharmaceutical and food products often involve the drying of aerosol droplets containing colloidal suspensions into powdered microparticles of desired properties. The morphology and surface properties of the final dry products/microparticles obtained after the drying process are strongly influenced by the parameters of the initial aerosol droplet composition and the drying conditions. In particular, the final dry microparticle morphology can be dependent on the dimensionless Péclet number (Pe), which expresses the relative competition between the diffusion of the dispersed particles within the droplet and the rate of solvent loss via evaporation. In this work, we examine how control over the gas phase drying conditions and initial aerosol droplet composition can be used to influence the aerosol droplet drying kinetics in the gas phase for a range of Péclet numbers. We used a single-particle levitation instrument, the electrodynamic balance, to measure the drying kinetics of colloidal silica droplets (0.10–0.60% v/v) under controlled gas phase drying conditions of temperature (263–326 K) and relative humidity (0–90%) and obtained Péclet numbers ranging from 4.05 to 184.5. We demonstrate that, for aerosol droplets with initially dilute feed colloid concentrations and within the constant evaporation regime, the starting composition does not strongly influence the solvent evaporation rate with the included nanoparticles (NPs) acting as spectators. However, the gas phase drying conditions, temperature, and relative humidity, directly influence the droplet temperature via evaporative cooling as well as the droplet drying kinetics and the final dry microparticle properties. With a priori knowledge of the droplet drying kinetics from the single droplet measurements, we further demonstrate the possibility of tailoring the morphology of the dried microparticles. Dried silica microparticles collected at Pe = 23.8 had dense spherical morphologies, while those at the highest Pe = 180.0 had crumpled surface morphologies with a transition in morphology between these limiting Pe values. Our results extend the fundamental understanding of the mechanisms controlling the drying of aerosol droplets in colloidal suspensions across a wide range of application areas extending from spray drying to the drying of respiratory fluid droplets containing bacteria and viruses and the drying of atmospheric aerosol droplets. more...
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- 2020
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11. Drying and Crystallization of Evaporating Sodium Nitrate Aerosol Droplets
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Rachael E. H. Miles, Jonathan P. Reid, C. P. Royall, Joshua F. Robinson, and Florence K. A. Gregson
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Materials science ,010304 chemical physics ,Evaporation ,Nucleation ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Aerosol ,law.invention ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,law ,Sodium nitrate ,Spray drying ,0103 physical sciences ,Materials Chemistry ,Physical and Theoretical Chemistry ,Crystallization - Abstract
The evaporation of liquid solution droplets and solute crystallization can be highly complex and is an important problem, particularly in spray drying where powdered products are produced from sprayed liquid droplets, such as in the food or pharmaceutical industries. In this work, we study the relationship between the evaporation rates of single levitated NaNO more...
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- 2020
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12. Analytical Challenges when Sampling and Characterising Exhaled Aerosol
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J. Archer, Fergus Hamilton, Jules Brown, Jonathan P. Reid, Henry E. Symons, Allen E. Haddrell, Sadiyah Sheikh, Jim S. Walker, Bryan R. Bzdek, Florence K. A. Gregson, and Christopher M. Orton
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Particle number ,Breathing ,Environmental Chemistry ,Environmental science ,Sampling (statistics) ,General Materials Science ,AERATOR ,Pollution ,Disease transmission ,Aerosol ,Remote sensing - Abstract
Respiratory particles produced by breathing, coughing, and speaking or generated during medical procedures serve as important routes for disease transmission. Characterising the number of particles generated as well as their size distribution is fundamental for guiding policy on infection control. However, sampling such particles carries inherent challenges. Respiratory particles are polydisperse in size, temporally and spatially variable, and emitted in very low concentrations, usually lower than the pre-existing aerosol concentration in indoor environments. In addition, they are typically emitted in a highly dynamic, warm and humid jet, leading to further rapid processes, such as dispersion and evaporation. Here, we discuss important considerations for sampling respiratory aerosol, focusing on sampling particles < 20 µm in diameter. Instruments capable of counting single-particles within this size range are commercially available. We provide recommendations for experimental protocols and demonstrate the limitations behind such approaches. We highlight the importance of a measurement space with as low a background aerosol concentration as possible, and of sampling for as long as possible to enable accurate quantitation of the size distribution of an aerosol plume. This is particularly important for the larger particles (> 5µm diameter) that are so low in concentration that they may require hours of sampling time to be accurately quantified. We explore the relationship between the flow rates of the exhalation and the sampling instrument and the consequent quantification of particle flux. We also discuss the transport and evaporation dynamics of liquid particles within respiratory jets, and their impacts on conducting aerosol sampling studies. more...
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- 2021
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13. Trileucine as a dispersibility enhancer of spray-dried inhalable microparticles
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Mark Nicholas, David Lechuga-Ballesteros, Jonathan P. Reid, Hui Wang, Mani Ordoubadi, Sandra Gracin, Reinhard Vehring, Nicholas B. Carrigy, Warren H. Finlay, and Florence K. A. Gregson
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Aerosols ,Materials science ,Aqueous solution ,Scanning electron microscope ,Dispersity ,Spray drying ,Particle formation ,Pharmaceutical Science ,Particle engineering ,Adsorption ,Chemical engineering ,Trileucine ,Desorption ,Administration, Inhalation ,Particle ,Particle Size ,Powders ,Particle density ,Oligopeptides ,Surface activity - Abstract
The formation of trileucine-containing spray-dried microparticles intended for pulmonary delivery was studied in depth. A single-particle method was employed to study the shell formation characteristics of trileucine in the presence of trehalose as a glass former, and an empirical correlation was proposed to predict the instance of shell formation. A droplet chain instrument was used to produce and collect monodisperse particles to examine morphology and calculate particle density for different levels of trileucine. It was observed that the addition of only 0.5 mg/mL (10% w/w) trileucine to a trehalose system could lower dried particle densities by approximately 1 g/cm3. In addition, a laboratory-scale spray dryer was used to produce batches of trileucine/trehalose powders in the respirable range. Raman spectroscopy demonstrated that both components were completely amorphous. Scanning electron microscopy and time-of-flight secondary ion mass spectrometry were used to study the particle morphologies and surface compositions. For all cases with trileucine, highly rugose particles with trileucine coverages of more than 60% by mass were observed with trileucine feed fractions of as little as 2% w/w. Moreover, it was seen that at lower trileucine content, smaller and larger particles of a polydisperse powder had slightly different surface compositions. The surface activity of trileucine was also modeled via a modified form of the diffusion equation inside an evaporating droplet that took into account initial surface adsorption and eventual surface desorption due to droplet shrinkage. Finally, using the Flory-Huggins theory, it was estimated that at room temperature, liquid-liquid phase separation would start when the trileucine reached an aqueous concentration of about 18 mg/mL. Besides the surface activity of trileucine, this low concentration was assumed to explain the substantial effect of trileucine on the morphology of spray-dried particles due to early phase separation. The methodology proposed in this study can be used in the rational design of trileucine-containing microparticles. more...
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- 2021
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14. A clinical observational analysis of aerosol emissions from dental procedures
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Tony Ireland, Andrew J Shrimpton, Jonathan P. Reid, Bryan R. Bzdek, Mark Gormley, Tom Dudding, Barry Main, Simon Haworth, Jennifer A Haworth, Sadiyah Sheikh, Fergus Hamilton, Florence K. A. Gregson, and Nick A Maskell more...
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ORTHODONTIC PROCEDURES ,business.industry ,Oral surgery ,Dental procedures ,Observational analysis ,Slow speed ,Dentistry ,Environmental science ,business ,Syringe ,Imaging phantom ,Aerosol - Abstract
Aerosol generating procedures (AGPs) are defined as any procedure releasing airborne particles σ)) and peak positions (DP,C)). The aerosol size distribution provided a robust fingerprint of aerosol emission from a source. 41 patients underwent fifteen different dental procedures. For nine procedures, no aerosol was detected above background. Where aerosol was detected, the percentage of procedure time that aerosol was observed above background ranged from 12.7% for ultrasonic scaling, to 42.9% for 3-in-1 air + water syringe. For ultrasonic scaling, 3-in-1 syringe use and surgical drilling, the aerosol size distribution matched the non-salivary contaminated instrument source, with no unexplained aerosol. High and slow speed drilling produced aerosol from patient procedures with different size distributions to those measured from the phantom head controls (mode widths log(σ)) and peaks (DP,C), p< 0.002) and, therefore, may pose a greater risk of salivary contamination. This study provides evidence for sources of aerosol generation during common dental procedures, enabling more informed evaluation of risk and appropriate mitigation strategies. more...
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- 2021
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15. Standard pleural interventions are not high-risk aerosol generating procedures
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Bryan R. Bzdek, Jonathan P. Reid, Nick A Maskell, Florence K. A. Gregson, Fergus Hamilton, George W Nava, Hugh F Welch, James W. Dodd, Alexandra S L Dipper, Sadiyah Sheikh, David T Arnold, and Amelia O Clive more...
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Pulmonary and Respiratory Medicine ,Infectious Disease Transmission, Patient-to-Professional ,Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ,medicine.medical_treatment ,Psychological intervention ,Thoracentesis ,Appropriate use ,complex mixtures ,03 medical and health sciences ,0302 clinical medicine ,Nothing ,medicine ,Humans ,030212 general & internal medicine ,Pandemics ,Agora ,Precautionary principle ,Aerosols ,business.industry ,Conflict of interest ,respiratory system ,Research Letters ,3. Good health ,Aerosol ,respiratory tract diseases ,030228 respiratory system ,Law ,Expert opinion ,Anesthesia ,Breathing ,Indwelling pleural catheter ,AERATOR ,business ,Production team - Abstract
The nosocomial spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has focused attention on the risk of aerosol generating procedures (AGPs) in healthcare [1]. SARS-CoV-2 has been isolated from pleural fluid, which has the potential to infect staff or patients if viraemic fluid is aerosolised during procedures [2, 3]. However, evidence for aerosol generation from pleural procedures is very limited. Current guidelines for appropriate use of personal protective equipment (PPE) while performing pleural procedures are based on expert opinion and application of the precautionary principle [4]. We set out to quantify if pleural procedures generated appreciable aerosol (aerosolised liquid particles that have the potential to carry virus) compared to aerosol sampled during normal respiratory activities of breathing and coughing., Percutaneous pleural procedures should not be considered aerosol generating. This study should inform future iterations of guidelines on the appropriate use of PPE when performing these procedures. https://bit.ly/3xFF71d more...
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- 2021
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16. Risk and mitigation of aerosolisation from lung function testing: results from the AERATOR study
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George W Nava, Jonathan P. Reid, James W. Dodd, Florence K. A. Gregson, Jules Brown, Bryan R. Bzdek, Sadiyah Sheikh, Fergus Hamilton, Riley C, Nick A Maskell, and David T Arnold
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Spirometry ,medicine.medical_specialty ,medicine.diagnostic_test ,Airway inflammation ,respiratory system ,Aerosol ,Pulmonary function testing ,Viral filter ,Internal medicine ,Breathing ,medicine ,Cardiology ,Environmental science ,Mouthpiece ,Lung function - Abstract
IntroductionLung function tests are fundamental diagnostic and monitoring tools for patients with respiratory symptoms. There is significant uncertainty around whether potentially infectious aerosol is produced during different lung function testing modalities; and limited data on possible mitigation strategies to reduce risk to staff and limit fallow time.MethodsHealthy volunteers were recruited in an ultraclean, laminar flow theatre and had standardised spirometry as per ERS/ATS guidance, as well as peak flow measurement and FENO assessment of airway inflammation. Aerosol emission was sampled minimum once each second using both an Aerodynamic Particle Sizer (APS) and Optical Particle Sizer (OPS), and compared to breathing, speaking and coughing. Mitigation strategies such as a peak flow viral filter and a CPET facemask (to mitigate induced coughing) were tested.Results33 healthy volunteers were recruited. Aerosol emission was highest in cough (1.61 particles/cm3/sample), followed by unfiltered peak flow (0.76 particles/cm3/sample). Filtered spirometry produced lower peak aerosol emission (0.11 particles/ cm3/sample) than that of a voluntary cough, and addition of a viral filter to the mouthpiece reduced peak flow aerosol emission to similar levels. The filter made little difference to recorded FEV peak flow values. Peak aerosol FENO measurement produced negligible aerosol. Reusable CPET masks with filter reduced aerosol emission when breathing, speaking, and coughing significantly.ConclusionsCompared to voluntary coughing, all lung function testing produced fewer aerosol particles. Filtered spirometry produces lower peak aerosol emission than peak voluntary coughing, and should not be deemed an aerosol generating procedure. The use of viral filters reduces aerosol emission in peak flow by > 10 times, and has little impact on recorded peak flow values. CPET masks are a useful option to reduce aerosol emission from induced coughing while performing spirometry. more...
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- 2021
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17. Comparing aerosol concentrations and particle size distributions generated by singing, speaking and breathing
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Lauren P. McCarthy, Christopher M. Orton, James D. F. Calder, Allen E. Haddrell, Declan Costello, Nick Gent, Jonathan P. Reid, Florence K. A. Gregson, Bryan R. Bzdek, Thomas Finnie, Gavin C. Donaldson, Pallav L. Shah, and Natalie A. Watson more...
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medicine.medical_specialty ,2019-20 coronavirus outbreak ,Technology ,Engineering, Chemical ,010504 meteorology & atmospheric sciences ,Coronavirus disease 2019 (COVID-19) ,viruses ,Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ,04 Earth Sciences ,Environmental Sciences & Ecology ,macromolecular substances ,010501 environmental sciences ,01 natural sciences ,09 Engineering ,Engineering ,Pandemic ,medicine ,Environmental Chemistry ,Meteorology & Atmospheric Sciences ,General Materials Science ,Tiina Reponen ,0105 earth and related environmental sciences ,Cultural sector ,Science & Technology ,musculoskeletal, neural, and ocular physiology ,virus diseases ,Pollution ,humanities ,Aerosol ,Engineering, Mechanical ,nervous system ,Emergency medicine ,Physical Sciences ,Breathing ,03 Chemical Sciences ,Life Sciences & Biomedicine ,Environmental Sciences ,psychological phenomena and processes - Abstract
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has resulted in an unprecedented shutdown in social and economic activity, with the cultural sector particularly severely affected. Restrictions on musical performances have arisen from a perception that there is a significantly higher risk of aerosol production from singing than speaking, based upon high-profile examples of clusters of COVID-19 following choral rehearsals. However, comparing aerosol generation from different types of vocalization, including singing, across a range of volumes is a rapidly evolving area of research. Here, we measured aerosols from singing, speaking and breathing from a large cohort of 25 professional singers in a range of musical genres in a zero-background environment, allowing unequivocal attribution of aerosol production to specific vocalizations. We do not assess the relative volumes at which people speak and sing. However, both showed steep increases in mass concentration with increase in loudness (spanning a factor of 20–30 across the dynamic range measured, p < 0.001). At the quietest volume (50 to 60 dBA), neither singing (p = 0.19) nor speaking (p = 0.20) were significantly different to breathing. At the loudest volume (90 to 100 dBA), a statistically significant difference (p < 0.001) was observed between singing and speaking, but with singing only generating a factor of between 1.5 and 3.4 more aerosol mass. Guidelines for musical performances should be based on the loudness and duration of the vocalization, the number of participants and the environment in which the activity occurs, rather than the type of vocalization. Mitigations such as the use of amplification and increased attention to ventilation should be employed where practicable. Copyright © 2021 American Association for Aerosol Research more...
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- 2021
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18. Aerosol emission from the respiratory tract: an analysis of relative risks from oxygen delivery systems
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Anna J Morley, Jonathan P. Reid, David T Arnold, Fergus Hamilton, Jules Brown, Ed Moran, Carolyn L. White, Sadiyah Sheikh, Nick A Maskell, Bryan R. Bzdek, James W. Dodd, Florence K. A. Gregson, and Ward K more...
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medicine.medical_specialty ,business.industry ,medicine.medical_treatment ,Exhalation ,Context (language use) ,Airborne transmission ,Aerosol ,medicine.anatomical_structure ,Relative risk ,Oxygen therapy ,Emergency medicine ,medicine ,Breathing ,business ,Respiratory tract - Abstract
BackgroundRisk of aerosolisation of SARS-CoV-2 directly informs organisation of acute healthcare and PPE guidance. Continuous positive airways pressure (CPAP) and high-flow nasal oxygen (HFNO) are widely used modes of oxygen delivery and respiratory support for patients with severe COVID-19, with both considered as high risk aerosol generating procedures. However, there are limited high quality experimental data characterising aerosolisation during oxygen delivery and respiratory support.MethodsHealthy volunteers were recruited to breathe, speak, and cough in ultra-clean, laminar flow theatres followed by using oxygen and respiratory support systems. Aerosol emission was measured using two discrete methodologies, simultaneously. Hospitalised patients with COVID-19 were also recruited and had aerosol emissions measured during breathing, speaking, and coughing.FindingsIn healthy volunteers (n = 25 subjects; 531 measures), CPAP (with exhalation port filter) produced less aerosols than breathing, speaking and coughing (even with large >50L/m facemask leaks). HFNO did emit aerosols, but the majority of these particles were generated from the HFNO machine, not the patient. HFNO-generated particles were small (InterpretationIn healthy volunteers, CPAP is associated with less aerosol emission than breathing, speaking or coughing. Aerosol emission from the respiratory tract does not appear to be increased by HFNO. Although direct comparisons are complex, cough appears to generate significant aerosols in a size range compatible with airborne transmission of SARS-CoV-2. As a consequence, the risk of SARS-CoV-2 aerosolisation is likely to be high in all areas where patients with Covid-19 are coughing. Guidance on personal protective equipment policy should reflect these updated risks.FundingNIHR-UKRI Rapid COVID call (COV003), Wellcome Trust GW4-CAT Doctoral Training Scheme (FH), MRC CARP Fellowship(JD, MR/T005114/1). Natural Environment Research Council grant (BB, NE/P018459/1)Research in contextEvidence before this studyPubMed was searched from inception until 10/1/21 using the terms ‘aerosol’, and variations of ‘non-invasive positive pressure ventilation’ and ‘high-flow nasal oxygen therapy’. Studies were included if they measured aerosol generated from volunteers or patients receiving non-invasive positive pressure ventilation (NIV) or high flow nasal oxygen therapy (HFNO), or provided experimental evidence on a simulated human setting. One study was identified (Gaeckle et al, 2020) which measured aerosol emission with one methodology (APS) but was limited by high background concentration of aerosol and a low number of participants (n = 10).Added value of this studyThis study used multiple methodologies to measure aerosol emission from the respiratory tract before and during CPAP and high-flow nasal oxygen, in an ultra-clean, laminar flow theatre with near-zero background aerosol and recruited patients with COVID-19 to ensure similar aerosol distributions. We conclude that there is negligible aerosol generation with CPAP, that aerosol emission from HFNO is from the machine and not the patient, coughing emits aerosols consistent with airborne transmission of SARS CoV2 and that healthy volunteers are a reasonable proxy for COVID-19 patients.Implications of all the available evidenceCPAP and HFNO should not be considered high risk aerosol generating procedures, based on our study and that of Gaeckle et al. Recorded aerosol emission from HFNO stems from the machine. Cough remains a significant aerosol risk. PPE guidance should be updated to ensure medical staff are protected with appropriate PPE in situations when patients with suspected or proven COVID-19 are likely to cough. more...
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- 2021
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19. Solid−Liquid Equilibria in Aqueous Solutions of Tris, Tris-NaCl, Tris- TrisHCl, and Tris-(TrisH)2SO4 at Temperatures from 5 to 45 °C
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Eric P. Achterberg, Florence K. A. Gregson, Jonathan P. Reid, Pablo Lodeiro, Simon L. Clegg, and David R. Turner
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Tris ,Ions ,Aqueous solution ,010504 meteorology & atmospheric sciences ,pH ,General Chemical Engineering ,Natural water ,Inorganic chemistry ,02 engineering and technology ,General Chemistry ,01 natural sciences ,6. Clean water ,chemistry.chemical_compound ,020401 chemical engineering ,chemistry ,Solubility ,13. Climate action ,Seawater ,0204 chemical engineering ,Solution chemistry ,Solid liquid ,0105 earth and related environmental sciences - Abstract
The substance Tris (or THAM, 2-amino-2-hydroxymethyl-1,3-propanediol) is used in the preparation of pH buffer solutions for applications in natural water chemistry, including seawater. The development of a chemical speciation model of buffer solutions containing Tris, TrisH+, and the major ions of seawater is desirable, so that the effects of changes in the composition and concentration of the medium on pH can be calculated. The Pitzer activity coefficient equations, commonly used in such speciation models, describe the thermodynamic properties of solutions in terms of interactions between dissolved ions and uncharged solute species. To determine some of these interactions, we have measured solubilities of Tris(s) in water and aqueous solutions of NaCl, TrisHCl, and (TrisH)2SO4 and the solubility of NaCl(s) in aqueous Tris(aq), from 5 to 45 °C. We report measurements of the water activities of Tris solutions at 293.5 K to high supersaturation with respect to the solid. Using the Pitzer equations, we compare our results to literature data yielding stoichiometric dissociation constants of TrisH+ in aqueous NaCl, and to electromotive forces of cells containing dissolved Tris, TrisHCl, and NaCl. Values of parameters for the interactions of Tris with the ions TrisH+, Na+, and SO42- at 25 °C are determined. The work of P.L. and E.P.A. was supported by the Helmholtz Association. The work of S.L.C. was supported by the Natural Environment Council of the UK, award number NE/P012361/1 under the joint NERC/NSF:GEO scheme. Authors F.K.A.G. and J.P.R. were supported by the Engineering and Physical Sciences Research Council under the grant code EP/N025245/1. This publication is a contribution of SCOR Working Group 145 (SCOR is the Scientific Committee on Oceanic Research) and of the Joint Committee on Seawater, which is sponsored by SCOR, the International Association for the Properties of Water and Steam, and the International Association for the Physical Sciences of the Oceans. The work of WG 145 presented in this article results, in part, from funding provided by national committees of SCOR and from a grant to SCOR from the U.S. National Science Foundation (OCE-1840868). more...
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- 2021
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20. Accurate Representations of the Microphysical Processes Occurring during the Transport of Exhaled Aerosols and Droplets
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Jonathan P. Reid, Sarah E. S. Michel, Florence K. A. Gregson, Jim S. Walker, J. Archer, and Bryan R. Bzdek
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Range (particle radiation) ,Microphysics ,010405 organic chemistry ,Chemistry ,Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ,General Chemical Engineering ,Analytical chemistry ,Evaporation ,General Chemistry ,Sedimentation ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Addition/Correction ,Phase (matter) ,Volume fraction ,Particle ,QD1-999 ,Research Article - Abstract
Aerosols and droplets from expiratory events play an integral role in transmitting pathogens such as SARS-CoV-2 from an infected individual to a susceptible host. However, there remain significant uncertainties in our understanding of the aerosol droplet microphysics occurring during drying and sedimentation and the effect on the sedimentation outcomes. Here, we apply a new treatment for the microphysical behavior of respiratory fluid droplets to a droplet evaporation/sedimentation model and assess the impact on sedimentation distance, time scale, and particle phase. Above a 100 μm initial diameter, the sedimentation outcome for a respiratory droplet is insensitive to composition and ambient conditions. Below 100 μm, and particularly below 80 μm, the increased settling time allows the exact nature of the evaporation process to play a significant role in influencing the sedimentation outcome. For this size range, an incorrect treatment of the droplet composition, or imprecise use of RH or temperature, can lead to large discrepancies in sedimentation distance (with representative values >1 m, >2 m, and >2 m, respectively). Additionally, a respiratory droplet is likely to undergo a phase change prior to sedimenting if initially, Accurate, experimentally derived microphysical treatments of respiratory fluid droplets enable the robust modeling of sedimentation outcomes. more...
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- 2021
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21. Aerosol and Droplet Generation from Performing with Woodwind and Brass Instruments
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Jonathan P. Reid, Christopher M. Orton, Florence K. A. Gregson, Natalie A. Watson, Lauren P. McCarthy, James D. F. Calder, Allen E. Haddrell, Bryan R. Bzdek, William J Browne, Declan Costello, and Pallav L. Shah more...
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2019-20 coronavirus outbreak ,aerosol generation ,Coronavirus disease 2019 (COVID-19) ,business.industry ,SARS-CoV-2 ,viruses ,Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ,virus diseases ,COVID-19 ,woodwinds ,macromolecular substances ,respiratory system ,complex mixtures ,Pollution ,Airborne transmission ,Virology ,Aerosol ,Environmental Chemistry ,Medicine ,General Materials Science ,airborne transmission ,business ,aerodynamic size - Abstract
The performing arts have been significantly restricted due to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. We report measurements of aerosol and droplet concentrations generated when playing woodwind and brass instruments and comparisons with breathing, speaking, and singing. These measurements were conducted in a room with zero number concentration aerosol background in the 0.5-20 µm diameter size range, allowing clear attribution of detected particles to specific activities. A total of 13 instruments were examined across 9 participants. Respirable particle number concentrations and size distributions for playing instruments are consistent with those from the participant when breathing, based on measurements with multiple participants playing the flute and piccolo as well as measurements across the entire cohort. Due to substantial interparticipant variability, we do not provide a comparative assessment of the aerosol generated by playing different instruments, instead considering only the variation in aerosol yield across all instruments studied. Both particle number and mass concentrations from playing instruments are lower than those from speaking and singing at high volume, and no large droplets >20 µm diameter are detected. Combined, these observations suggest that playing instruments generates less aerosol than speaking or singing at high volumes. Moreover, there is no difference between the aerosol concentrations generated by professional and amateur performers while breathing, speaking, or singing, suggesting conclusions for professional singers may also apply to amateurs. more...
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- 2021
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22. How effective are face coverings in reducing transmission of COVID-19?
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Joshua F. Robinson, Ioatzin Rios de Anda, Fergus J. Moore, Florence K. A. Gregson, Jonathan P. Reid, Lewis Husain, Richard P. Sear, and C. Patrick Royall
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Biological Physics (physics.bio-ph) ,Fluid Dynamics (physics.flu-dyn) ,Environmental Chemistry ,Soft Condensed Matter (cond-mat.soft) ,FOS: Physical sciences ,General Materials Science ,Physics - Biological Physics ,Physics - Fluid Dynamics ,Condensed Matter - Soft Condensed Matter ,Pollution - Abstract
In the COVID-19 pandemic, billions are wearing face masks, in both health care settings and in public. Which type of mask we should wear in what situation, is therefore important. There are three basic types: cotton, surgical, and respirators (e.g. FFP2, N95 and similar). All are essentially air filters worn on the face. Air filtration is relatively well understood, however, we have almost no direct evidence on the relative role played by aerosol particles of differing sizes in disease transmission. But if the virus concentration is assumed independent of aerosol particle size, then most virus will be in particles > 1 $��$m. We develop a model that predicts surgical masks are effective at reducing the risk of airborne transmission because the filtering material most surgical masks use is highly effective at filtering particles with diameters > 1 $��$m. However, surgical masks are significantly less effective than masks of FFP2, N95 and similar standards, mostly due to the poor fit of surgical masks. Earlier work found that ~30% of the air bypasses a surgical mask and is not filtered. This highlights the fact that standards for surgical masks do not specify how well the mask should fit, and so are not adequate for protection against COVID-19., 11 pages + references, 7 figures. Resubmitted version with substantial additions over original more...
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- 2020
23. A quantitative evaluation of aerosol generation during tracheal intubation and extubation
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Jules Brown, Bryan R. Bzdek, Jonathan P. Reid, Andrew J Shrimpton, Tim Cook, Florence K. A. Gregson, and Anthony E. Pickering
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Operating Rooms ,medicine.medical_treatment ,law.invention ,0302 clinical medicine ,030202 anesthesiology ,law ,Extubation ,Intubation ,Medicine ,Anesthesia ,030212 general & internal medicine ,Prospective Studies ,Airway Management ,aerosol‐generating procedure ,Covid19 ,respiratory system ,Ventilation (architecture) ,Original Article ,Risk assessment ,AERATOR ,Environmental Monitoring ,SARS‐COV‐2 ,2019-20 coronavirus outbreak ,extubation ,Coronavirus disease 2019 (COVID-19) ,Patients ,Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ,UNCOVER ,SARS-COV-2 ,Airway Extubation ,intubation ,03 medical and health sciences ,COVID‐19 ,Correspondence ,Intubation, Intratracheal ,Humans ,Particle Size ,Personal protective equipment ,Personal Protective Equipment ,Aerosols ,business.industry ,SARS-CoV-2 ,Tracheal intubation ,COVID-19 ,Original Articles ,Respiration, Artificial ,Ventilation ,Aerosol ,Anesthesiology and Pain Medicine ,Cough ,Aerosol Generating Procedure ,Anesthetists ,Airway management ,business ,Anaesthesia Pain and Critical Care - Abstract
The potential aerosolised transmission of severe acute respiratory syndrome coronavirus-2 is of global concern. Airborne precaution personal protective equipment and preventative measures are universally mandated for medical procedures deemed to be aerosol generating. The implementation of these measures is having a huge impact on healthcare provision. There is currently a lack of quantitative evidence on the number and size of airborne particles produced during aerosol-generating procedures to inform risk assessments. To address this evidence gap, we conducted real-time, high-resolution environmental monitoring in ultraclean ventilation operating theatres during tracheal intubation and extubation sequences. Continuous sampling with an optical particle sizer allowed characterisation of aerosol generation within the zone between the patient and anaesthetist. Aerosol monitoring showed a very low background particle count (0.4 particles.l−1) allowing resolution of transient increases in airborne particles associated with airway management. As a positive reference control, we quantitated the aerosol produced in the same setting by a volitional cough (average concentration, 732 (418) particles.l−1, n = 38). Tracheal intubation including facemask ventilation produced very low quantities of aerosolised particles (average concentration, 1.4 (1.4) particles.l−1, n = 14, p < 0.0001 vs. cough). Tracheal extubation, particularly when the patient coughed, produced a detectable aerosol (21 (18) l−1, n = 10) which was 15-fold greater than intubation (p = 0.0004) but 35-fold less than a volitional cough (p < 0.0001). The study does not support the designation of elective tracheal intubation as an aerosol-generating procedure. Extubation generates more detectable aerosol than intubation but falls below the current criterion for designation as a high-risk aerosol-generating procedure. These novel findings from real-time aerosol detection in a routine healthcare setting provide a quantitative methodology for risk assessment that can be extended to other airway management techniques and clinical settings. They also indicate the need for reappraisal of what constitutes an aerosol-generating procedure and the associated precautions for routine anaesthetic airway management. more...
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- 2020
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24. On the particle formation of leucine in spray drying of inhalable microparticles
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Jonathan P. Reid, Mani Ordoubadi, Florence K. A. Gregson, Mark Nicholas, Sandra Gracin, Warren H. Finlay, Reinhard Vehring, Hui Wang, and David Lechuga-Ballesteros
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Materials science ,Nucleation ,Pharmaceutical Science ,02 engineering and technology ,030226 pharmacology & pharmacy ,law.invention ,03 medical and health sciences ,symbols.namesake ,Crystallinity ,0302 clinical medicine ,law ,Leucine ,Administration, Inhalation ,Crystallization ,Particle Size ,Aerosols ,Quantitative Biology::Biomolecules ,Supersaturation ,Spray Drying ,021001 nanoscience & nanotechnology ,Chemical engineering ,Spray drying ,symbols ,Particle ,Particle size ,Powders ,0210 nano-technology ,Raman spectroscopy - Abstract
The particle formation of L-leucine, a dispersibility-enhancing amino acid used in the spray drying of inhalable pharmaceutical aerosols, was extensively studied using three experimental methods, and the results were interpreted with the aid of theory. A comparative-kinetics electrodynamic balance was used to study the shell formation behavior in single evaporating microdroplets containing leucine and trehalose. Different concentration thresholds of solidification and shell formation were determined for trehalose and leucine, which were then used in the particle formation model to predict the properties of spray-dried particles. Furthermore, a droplet chain instrument was used to study the particle morphologies and particle densities that were not accessible in the single particle experiments. Lab-scale spray drying was also used to produce powders typical for actual pharmaceutical applications. Raman spectroscopy confirmed that a glass former, such as trehalose, can inhibit the crystallization of leucine. The surface compositions of these spray-dried powders were analyzed via time-of-flight secondary ion mass spectrometry. The leucine surface coverage in a polydisperse powder was determined to be a function of the particle size or the initial droplet diameter of each respective particle. This observation confirms the important role of leucine crystallization kinetics in its shell-forming capabilities. A critical supersaturation ratio of 3.5 was also calculated for leucine, at which it is assumed to instantaneously nucleate out of solution. This ratio was used as the threshold for the initiation of crystallization. Crystallinity predictions for the leucine-trehalose particles based on this supersaturation ratio were in good agreement with the solid-state characterizations obtained by Raman spectroscopy. This study improves the fundamental understanding of the particle formation process of leucine-containing formulations, which can apply to other crystallizing systems and potentially facilitate the rational design of such formulations with reduced experimental effort. more...
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- 2020
25. Evaluation of the comparative risk of aerosol generation by tracheal intubation and extubation in the operating theatre
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Jules Brown, Jonathan P. Reid, Bryan R. Bzdek, Anthony E. Pickering, Florence K. A. Gregson, and Andrew J Shrimpton
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medicine.medical_specialty ,medicine.diagnostic_test ,Operating theatres ,business.industry ,medicine.medical_treatment ,Laryngoscopy ,Tracheal intubation ,Endotracheal intubation ,law.invention ,Aerosol ,law ,Anesthesia ,Emergency medicine ,Ventilation (architecture) ,medicine ,Airway management ,Risk assessment ,business ,Personal protective equipment ,Aerosolization - Abstract
Background: Transmission of SARS-CoV-2 by bioaerosols is of increasing concern. The enhanced levels of personal protective equipment (PPE) and preventative measures to attenuate viral transmission during aerosol generating procedures (AGPs) are having a huge impact on healthcare provision. There is no quantitative evidence on the number and size of airborne particles produced during AGPs to inform risk assessments. Methods: Real-time, high-resolution environmental monitoring was conducted in ultraclean ventilation operating theatres. Continuous sampling with an optical particle sizer allowed characterisation of aerosol generation within the airway management zone during endotracheal intubation and extubation for urgent orthopaedic trauma or neuro-surgery. Findings: Aerosol monitoring showed a very low background particle count allowing resolution of the transient airborne particle plume produced by reference volitional coughs (maximum concentration, 1,690±140 particles.L‑1,n=38). By comparison, endotracheal intubation including mask ventilation produced negligible quantities of aerosolised particles (maximum concentration, 80±10 L‑1,n=14, P more...
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- 2020
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26. Studies of competing evaporation rates of multiple volatile components from a single binary-component aerosol droplet
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Mani Ordoubadi, David Barona, Jonathan P. Reid, Allen E. Haddrell, David Lewis, Tanya Church, Rachael E. H. Miles, Reinhard Vehring, and Florence K. A. Gregson
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Range (particle radiation) ,Materials science ,Microphysics ,Condensation ,Evaporation ,General Physics and Astronomy ,02 engineering and technology ,Radius ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Aerosol ,Physics::Fluid Dynamics ,13. Climate action ,Chemical physics ,Relative humidity ,Physical and Theoretical Chemistry ,0210 nano-technology ,Physics::Atmospheric and Oceanic Physics ,Evaporative cooler - Abstract
The simultaneous evaporation and condensation of multiple volatile components from multicomponent aerosol droplets leads to changes in droplet size, composition and temperature. Measurements and models that capture and predict these dynamic aerosol processes are key to understanding aerosol microphysics in a broad range of contexts. We report measurements of the evaporation kinetics of droplets (initially ∼25 μm radius) formed from mixtures of ethanol and water levitated within a electrodynamic balance over timescales spanning 500 ms to 6 s. Measurements of evaporation into a gas phase of varied relative humidity and temperature are shown to compare well with predictions from a numerical model. We show that water condensation from the gas phase can occur concurrently with ethanol evaporation from aqueous-ethanol droplets. Indeed, water can condense so rapidly during the evaporation of a pure ethanol droplet in a humid environment, driven by the evaporative cooling the droplet experiences, that the droplet becomes pure water within 0.4 s. more...
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- 2019
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27. Drying kinetics and nucleation in evaporating sodium nitrate aerosols
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Jonathan P. Reid, Florence K. A. Gregson, Rachael E. H. Miles, C. Patrick Royall, and Joshua F. Robinson
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Aqueous solution ,Materials science ,010304 chemical physics ,nucleation ,Nucleation ,Evaporation ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,6. Clean water ,0104 chemical sciences ,law.invention ,Aerosol ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Sodium nitrate ,law ,colloids ,Spray drying ,0103 physical sciences ,Classical nucleation theory ,Physical and Theoretical Chemistry ,Crystallization ,aerosols - Abstract
A quantitative understanding of the evaporative drying kinetics and nucleation rates of aqueous based aerosol droplets is important for a wide range of applications, from atmospheric aerosols to industrial processes such as spray drying. Here, we introduce a numerical model for interpreting measurements of the evaporation rate and phase change of drying free droplets made using a single particle approach. We explore the evaporation of aqueous sodium chloride and sodium nitrate solution droplets. Although the chloride salt is observed to reproducibly crystallize at all drying rates, the nitrate salt solution can lose virtually all of its water content without crystallizing. The latter phenomenon has implications for our understanding of the competition between the drying rate and nucleation kinetics in these two systems. The nucleation model is used in combination with the measurements of crystallization events to infer nucleation rates at varying equilibrium state points, showing that classical nucleation theory provides a good description of the crystallization of the chloride salt but not the nitrate salt solution droplets. The reasons for this difference are considered. more...
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- 2020
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28. Aerosol generation during percutaneous tracheostomy insertion
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Jules Brown, Ivan Collin, Aravind V Ramesh, and Florence K. A. Gregson
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2019-20 coronavirus outbreak ,medicine.medical_specialty ,Coronavirus disease 2019 (COVID-19) ,business.industry ,Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ,medicine ,Percutaneous tracheostomy ,Brief Communications ,Critical Care and Intensive Care Medicine ,Critical Care Nursing ,business ,Surgery - Published
- 2020
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29. Correction to: Multi-Solvent Microdroplet Evaporation: Modeling and Measurement of Spray-Drying Kinetics with Inhalable Pharmaceutics
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Jonathan P. Reid, David Lechuga-Ballesteros, Sandra Gracin, Mani Ordoubadi, Rachael E. H. Miles, David Barona, Reinhard Vehring, Omar Melhem, Dexter D’Sa, Florence K. A. Gregson, and Warren H. Finlay
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Pharmacology ,Materials science ,Organic Chemistry ,Pharmacology toxicology ,Kinetics ,Evaporation ,Pharmaceutical Science ,Solvent ,Chemical engineering ,Spray drying ,Molecular Medicine ,Pharmaceutics ,Pharmacology (medical) ,Biotechnology - Abstract
The Publisher regrets having introduced the following errors into the article when performing proof corrections.
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- 2019
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30. Multi-Solvent Microdroplet Evaporation:Modeling and Measurement of Spray-Drying Kinetics with Inhalable Pharmaceutics
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Sandra Gracin, Jonathan P. Reid, Dexter D’Sa, Mani Ordoubadi, Omar Melhem, David Lechuga-Ballesteros, Warren H. Finlay, Rachael E. H. Miles, David Barona, Florence K. A. Gregson, and Reinhard Vehring
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Materials science ,particle engineering ,Dispersity ,Evaporation ,Pharmaceutical Science ,02 engineering and technology ,Péclet number ,030226 pharmacology & pharmacy ,law.invention ,Excipients ,03 medical and health sciences ,symbols.namesake ,0302 clinical medicine ,Leucine ,law ,Azeotrope ,Administration, Inhalation ,inhaled therapeutics ,Pharmacology (medical) ,Desiccation ,Budesonide ,Distillation ,co-solvents ,Pharmacology ,microparticles ,Ethanol ,Nebulizers and Vaporizers ,Organic Chemistry ,Beclomethasone ,Trehalose ,Water ,multi-solvent spray-drying ,021001 nanoscience & nanotechnology ,6. Clean water ,Solvent ,Kinetics ,Chemical engineering ,Spray drying ,Solvents ,symbols ,Quantum Theory ,Molecular Medicine ,Particle ,Powders ,0210 nano-technology ,Biotechnology - Abstract
Purpose: Evaporation and particle formation from multi-solvent microdroplets containing solid excipients pertaining to spray-drying of therapeutic agents intended for lung delivery were studied. Various water and ethanol co-solvent systems containing a variety of actives and excipients (beclomethasone, budesonide, leucine, and trehalose) were considered. Methods: Numerical methods were used to predict the droplet evaporation rates and internal solute transfers, and their results verified and compared with results from two separate experimental setups. In particular, an electrodynamic balance was used to measure the evaporation rates of multicomponent droplets and a monodisperse droplet chain setup collected dried microparticles for further analytical investigations and ultramicroscopy. Results: The numerical results are used to explain the different particle morphologies dried from solutions at different co-solvent compositions. The obtained numerical data clearly show that the two parameters controlling the general morphology of a dried particle, namely the Péclet number and the degree of saturation, can change with time in a multi-solvent droplet. This fact complicates product development for such systems. However, this additional complexity vanishes at what we define as the iso-compositional point, which occurs when the solvent ratios and other composition-dependent properties of the droplet remain constant during evaporation, similar to the azeotrope of such systems during distillation. Conclusions: Numerical and experimental analysis of multi-solvent systems indicate that spray-drying near the iso-compositional ratio simplifies the design and process development of such systems. more...
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- 2019
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31. Drying Kinetics of Salt Solution Droplets: Water Evaporation Rates and Crystallization
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C. P. Royall, Rachael E. H. Miles, Jonathan P. Reid, Joshua F. Robinson, and Florence K. A. Gregson
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endocrine system ,Materials science ,Diffusion ,Nucleation ,Evaporation ,010402 general chemistry ,01 natural sciences ,complex mixtures ,law.invention ,Physics::Fluid Dynamics ,law ,Phase (matter) ,0103 physical sciences ,Materials Chemistry ,Physics::Atomic and Molecular Clusters ,Physical and Theoretical Chemistry ,Crystallization ,Physics::Atmospheric and Oceanic Physics ,Supersaturation ,Aqueous solution ,010304 chemical physics ,technology, industry, and agriculture ,eye diseases ,0104 chemical sciences ,Surfaces, Coatings and Films ,Aerosol ,Chemical engineering - Abstract
Drying and crystallization of solution droplets is a problem of broad relevance, determining the microstructures of particles formed in spray-drying, the phase of particles delivered by, for example, aerosol formulations for inhalation therapies, and the impact of aerosols on radiative forcing and climate. The ephemeral nature of free droplets, particularly when considering the drying kinetics of droplets with highly volatile constituents, has often precluded the accurate measurement of transient properties such as droplet size and composition, preventing the robust assessment of predictive models of droplet-drying rates, nucleation, and crystallization. Here, we report novel measurements of the drying kinetics of individual aqueous sodium chloride solution droplets using an electrodynamic balance to isolate and trap single aerosol droplets (radius ≈ 25 μm). The initial solution droplet size and composition are shown to be highly reproducible in terms of drying rate and crystallization time when examined over hundreds of identical evaporating droplets. We introduce a numerical model that determines the concentration gradient across the radial profile of the droplet as it dries, considering both the surface recession because of evaporation and the diffusion of components within the droplet. Drying-induced crystallization is shown to be fully determined for this system, with nucleation and instantaneous crystallization occurring once a critical supersaturation level of 2.04 ± 0.02 is achieved at the surface of the evaporating droplet. This phenomenological model provides a consistent account of the timescale and surface concentration of free-droplet crystallization on drying for the different drying conditions studied, a necessary step in progress toward achieving control over rates of crystallization and the competitive formation of amorphous particles. more...
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- 2018
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32. Aerosol emission from the respiratory tract: an analysis of aerosol generation from oxygen delivery systems
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Kirsty Ward, Carrie White, Anna J Morley, Jules Brown, Jonathan P. Reid, David T Arnold, Nick A Maskell, Fergus Hamilton, James W. Dodd, Florence K. A. Gregson, Bryan R. Bzdek, Ed Moran, and Sadiyah Sheikh more...
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Pulmonary and Respiratory Medicine ,medicine.medical_treatment ,Respiratory System ,Humans ,Medicine ,Continuous positive airway pressure ,Respiratory system ,Aerosols ,SARS-CoV-2 ,business.industry ,COVID-19 ,Exhalation ,Respiratory infection ,respiratory system ,respiratory tract diseases ,Aerosol ,Oxygen ,medicine.anatomical_structure ,Anesthesia ,Breathing ,Oxygen delivery ,AERATOR ,business ,Anaesthesia Pain and Critical Care ,Respiratory tract - Abstract
Introductioncontinuous positive airway pressure (CPAP) and high-flow nasal oxygen (HFNO) provide enhanced oxygen delivery and respiratory support for patients with severe COVID-19. CPAP and HFNO are currently designated as aerosol-generating procedures despite limited high-quality experimental data. We aimed to characterise aerosol emission from HFNO and CPAP and compare with breathing, speaking and coughing.Materials and methodsHealthy volunteers were recruited to breathe, speak and cough in ultra-clean, laminar flow theatres followed by using CPAP and HFNO. Aerosol emission was measured using two discrete methodologies, simultaneously. Hospitalised patients with COVID-19 had cough recorded using the same methodology on the infectious diseases ward.ResultsIn healthy volunteers (n=25 subjects; 531 measures), CPAP (with exhalation port filter) produced less aerosol than breathing, speaking and coughing (even with large >50 L/min face mask leaks). Coughing was associated with the highest aerosol emissions of any recorded activity. HFNO was associated with aerosol emission, however, this was from the machine. Generated particles were small (ConclusionsIn healthy volunteers, standard non-humidified CPAP is associated with less aerosol emission than breathing, speaking or coughing. Aerosol emission from the respiratory tract does not appear to be increased by HFNO. Although direct comparisons are complex, cough appears to be the main aerosol-generating risk out of all measured activities. more...
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